Process employing cooling in a static atmosphere for high permeability silicon steel comprising copper

ABSTRACT

A process for producing silicon steel having a cube-on-edge orientation and a permeability of at least 1850 (G/Oe) at 10 oersteds, which includes the steps of: preparing a melt of steel consisting essentially of, by weight, up to 0.07% carbon, from 2.60 to 4.0% silicon, from 0.03 to 0.24% manganese, at least 0.01% selenium, from 0.01 to 0.09% of material from the group consisting of sulfur and selenium, from 0.015 to 0.04% aluminum, up to 0.02% nitrogen, from 0.1 to 0.5% copper, balance iron; casting the steel; hot rolling the steel; annealing the steel prior to a final cold roll at a temperature of from 1400* to 2150*F; cooling the steel from a temperature below 1700*F and above 750*F to a temperature at least as low as 500*F with a liquid quenching medium or gaseous stream and from its maximum annealing temperature to the temperature below 1700*F and above 750*F at a rate which is no faster than one wherein the steel is cooled in a static atmosphere or in a continuous processing line where there is some relative motion between the atmosphere and the steel, although the only deliberate motion is that imparted to the steel; and cold rolling the steel at a reduction of at least 80%.

United States Patent 1 Salsgiver et a].

1 PROCESS EMPDOYING COOLING IN A STATIC ATMOSPHERE FOR HIGH PERMEABILITY SILICON STEEL COMPRISING COPPER [75] Inventors: James A. Salsgiver, Sarver; Frank A.

Malagari, Freeport, both of Pa.

[73] Assignee: Allegheny Ludlum Industries, Inc.,

Pittsburgh, Pa.

[22] Filed: Nov. 18, 1974 [21] Appl. No.: 524,831

[52] 11.8. C1. 148/112; 75/123 L; 148/121 [51] Int. Cl. H01F 1/04 [58] Field ()l'search 148/112, 111, 110,120, 148/121, 31.55, 75/123 L [561 References Cited UNITED STATES PATENTS 3,287,184 11/1966 Koh 148/111 3,632,456 l/l972 Sakakura et a1 148/111 3,671,337 6/1972 Kumai et a1. 148/112 3,764,406 10/1973 Littmann 148/111 3,770,517 11/1973 Gray et a1. 148/111 3,855,018 12/1974 Salsgiver et al..... 148/112 3,855,019 12/1974 Salsgiver et al..... 148/112 3,855,020 12/1974 Salsgiver et a1 148/112 3,855,021 12/1974 Salsgiver et a1. 148/112 OTHER PU BLICATIONS Saito, A.; Effect of Minor Elements in Silicon Steel; in Nippon Kinzokv, 27, 1963, pp. l91l95.

[ Dec.9, 1975 Kussmann, A.; Gekupferter Sta/21 Fur Transform; in Sta/11 und Eisen; 1930, pp. l1941l97.

Primary ExaminerWalter R. Satterfield Attorney, Agent, or Firm-Vincent G. Gioia; Robert F. Dropkin 1 1 ABSIRACT A process for producing silicon steel having a cubeon-edge orientation and a permeability of at least 1850 (G/O at 10 oersteds, which includes the steps of: preparing a melt of steel consisting essentially of, by weight, up to 0.07% carbon, from 2.60 to 4.0% silicon, from 0.03 to 0.24% manganese, at least 0.01% selenium, from 0.01 to 0.09% of material from the group consisting of sulfur and selenium, from 0.015 to 0.04% aluminum, up to 0.02% nitrogen, from 0.1 to 0.5% copper, balance iron; casting the steel; hot rolling the steel; annealing the steel prior to a final cold roll at a temperature of from l400 to 2150F; cooling the steel from a temperature below 1700F and above 750F to a temperature at least as low as 500F with a liquid quenching medium or gaseous stream and from its maximum annealing temperature to the temperature below 1700F and above 750F at a rate which is no faster than one wherein the steel is cooled in a static atmosphere or in a continuous processing line where there is some relative motion between the at mosphere and the steel, although the only deliberate motion is that imparted to the steel; and cold rolling the steel at a reduction of at least 80%.

15 Claims, No Drawings PROCESS EMPLOYING COOLING IN A STATIC ATMOSPHERE FOR HIGH PERMEABILITY SILICON STEEL COMPRISING COPPER The present invention relates to a process for producing electromagnetic silicon steel having a cube-on-edge orientation and a permeability of at least 1850 (6/0 at oersteds.

Oriented silicon steels containing 2.60 to 4.0% silicon are generally produced by processes which involve hot rolling, a double cold reduction, an anneal before each cold roll and a high temperature texture anneal. Characterizing these steels are permeabilities at 10 oersteds of from about 1790 to 1840 (6/0,).

in recent years a number of patents have disclosed methods for producing silicon steels with permeabilities in excess of 1850 (6/0 at 10 oersteds. Of these US. Pat. Nos. 3,287,183, 3,632,456 and 3,636,579 appear to be the most interesting. A still more interesting method is, however, described in a copending US. patent application. The application, Ser. No. 357,974, was filed on May 7, 1973 in the names of James A. Salsgiver and Frank A. Malagari. Application Ser. No. 357,974 describes a process which includes the steps of: preparing a melt of steel consisting essentially of, by weight, up to 0.07% carbon, from 2.6 to 4.0% silicon, from 0.03 to 0.24% manganese, from 0.01 to 0.07% sulfur, from 0.015 to 0.04% aluminum, up to 0.02% nitrogen, from 0.1 to 0.5% copper, balance iron; casting the steel; hot rolling the steel; annealing the steel prior to a final cold roll at a temperature of from 1400" to 2150F; cooling the steel from a temperature below 1700F and about 750F to a temperature at least as low as 500F with a liquid quenching medium or gaseous stream and from its maximum annealing temperature to the temperature below 1700F and above 750F at a rate which is no faster than one wherein the steel is cooled in a static atmosphere or in a continuous processing line where there is some relative motion between the atmosphere and the steel, although the only deliverate motion is that imparted to the steel; and cold rolling the steel at a reduction of at least 80%.

Described herein is another, and improved method for producing silicon steel having a cube-on-edge orientation and a permeability of at least 1850 (6/0 at 10 oersteds. It is primarily based upon the discovery that the melt of application Ser. No. 357,974 can be prepared with selenium replacing part or all of the sulfur contained therein.

It is accordingly an object of the present invention to provide a process for producing electromagnetic silicon steel having a cube-on-edge orientation and a permeability of at least 1850 (6/0,) at 10 oersteds.

The present invention provides a method for producing silicon steel having a cube-on-edge orientation and a permeability of at least 1850 (G/O,,) at 10 oersteds. lnvolved therein are the steps of: preparing a melt of silicon steel consisting essentially of, by weight, up to 0.07% carbon, from 2.60 to 4.0% silicon, from 0.03 to 0.24% manganese, at least 0.01% selenium, from 0.01 to 0.09% of material from the group consisting of sulfur and selenium, from 0.015 to 0.04% aluminum, up to 0.02% nitrogen, from 0.1 to 0.5% copper, balance iron; casting the steel; hot rolling the steel into a hot rolled band; subjecting the steel to at least one cold rolling; subjecting the steel to final annealing prior to the final cold rolling; decarburizing the steel; and final texture annealing the steel. Aslo included, and significantly so,

are the specific steps of: carrying out the final anneal prior to the final cold rolling at a temperature of from 1400 to 2150F for a period of from 15 seconds to 2 hours; cooling the steel from a temperature below l700F and above 750F to a temperature at least as low as 500F with a liquid quenching medium or gaseous stream and from its maximum annealing temperature to the temperature below 1700F and above 750F at a rate which is no faster than one wherein the steel is cooled in a static atmosphere or in a continuous processing line where there is some relative motion between the atmosphere and the steel, although the only deliverate motion is that imparted to the steel; and cold rolling the cooled steel at a reduction of at least Preferred conditions include annealing at a temperature of from l800 to 2125F, cooling with a liquid quenching medium or gaseous stream from a temperature below l600F and above 1000F, and cold rolling at a reduction of at least Melting, casting, hot rolling, cold rolling, decarburizing and final texture annealing do not involve any novel procedure, as far as techniques are concerned, and with regard to them, the invention encompasses all applicable steelmaking procedures. As to the cold rolling, it should, however, be pointed out that several roll passes can constitute a single cold rolling operation, and that plural cold rolling operations exist only when cold rolling passes are separated by an anneal.

The steel melt must include silicon, aluminum, manganese and selenium. Silicon is necessary as it increases the steels resistivity, decreases its magnetostriction, decreases its magnetocrystalline anisotropy and hence decreases its core loss. Aluminum, manganese and selenium are necessary as they form inhibitors which are essential for controlling the steels orientation and its properties which are dependent thereon. More specifically, aluminum combines with nitrogen in the steel or from the atmosphere, to form aluminum nitride; and manganese combines with selenium, and possibly copper, to form manganese selenide and/or manganese copper selenide, and with sulfur if it is present, to form manganese sulfide and/or manganese copper sulfide. All together, these compounds inhibit normal grain growth during the final texture anneal, while at the same time aiding in the development of secondary recrystallized grains having the desired cube-on-edge orientation. Copper, noted above for its presence in manganese inhibitors, can also be beneficial during processing. It is hypothesized that copper can lower the annealing temperature, lower the temperature from which the rapid cool can occur, improve rollability, simplify melting, and relax annealing atmosphere requirements. Moreover, copper increases the steels resistivity and decreases its core loss.

A steel in which the process of the present invention is particularly adaptable to consists essentially of, by weight, from 0.02 to 0.0 7% carbon, from 2.65 to 3.25% silicon, from 0.05 to 0.20% manganese, at least 0.02% selenium, from 0.02 to 0.07% of material from the group consisting of sulfur and selenium, from 0.015 to 0.04% aluminum, from 0.0030 to 0.0090% nitrogen, from 0.1 to 0.4% copper, balance iron. This steel has its chemistry balanced so as to produce a highly beneficial structure when processed according to the present invention.

Although we are not sure why the final anneal prior to the final cold rolling, and the controlled cooling of the present invention is so beneficial, we hypothesize:

3 that the anneal conditions the steel for cold rolling and provides an operation during which inhibitors can form; and that the slow cool to a temperature below l700F and/or the use of annealing temperatures in the lower part of the annealing temperature range, increase the uniformity in which the inhibitors are distributed, as essentially only ferrite phase is present in the steel at temperatures below l700F, contrasted to the presence of austenite and ferrite phases and different solubilities cessing line where there is some relative motion be' tween the atmosphere and the steel, although the only deliberate motion is that imparted to the steel; and cold rolling the cooled steel at a reduction of at least 80%; said melt consisting essentially of, by weight, up to 0.07% carbon, from 2.60 to 4.0% silicon, from 0.03 to 0.24% manganese, at least 0.0l% selenium, from 0.0l to 0.09% of material from the group consisting of sulfur and selenium, from 0.015 to 0.04% aluminum, up to for the inhibiting elements in each phase at somewhat 0.02% nitrogen, from 0.1 to 0.5% copper, balance iron. higher temperatures. As discussed above, the primary 2. An improvement according to claim 1, wherein inhibitors are aluminum nitride, and compounds of said steel is cooled from a temperature below 1600F manganese selenide and possibly manganese sulfide. and above 1000F to a temperature at least as low as No criticality is placed upon the particular annealing 500F with a liquid quenching medium or gaseous atmosphere. Illustrative atmosphere therefore include stream and from its maximum annealing temperature nitrogen; reducing gases such as hydrogen; inert gases to said temperature below 1600F and above l000F at such as argon; air; and mixtures thereof. a rate which is no faster than one wherein the steel is The following example is illustrative of several ascooled in a static atmosphere or in a continuous propects of the invention. cessing line where there is some relative motion be- A heat of steel was cast and processed into silicon tween the atmosphere and the steel, although the only steel having a cube-on-edge orientation. The chemistry deliberate motion is that imparted to the steel. of the heat appears hereinbelow in the Table. 3. An improvement according to claim 1, wherein TABLE Composition (wt.

C Mn Si Se S Al Cu N Fe 0.066 0.13 2.77 0.056 0.013 0.028 0.4 0.0068 Ba].

Processing for the heat involved soaking at an elevated temperature for several hours, hot rolling to a gage of said final anneal prior to the final cold rolling is at a approximately 93 mils, heat treating for 1 minute at temperature of from l800 to 2l25F. 2050F, slow cooling to l740F (approximately 50 sec- 4. An improvement according to claim 3, wherein onds), air cooling to ll00F, water quenching from said steel is cooled from a temperature l600F and l 100F, cold rolling to a final gage of approximately 12 above l000F to a temperature at least as low as 500F mils, decarburizing at a temperature of 1475F in a with a liquid quenching medium or gaseous stream and mixture of wet hydrogen and nitrogen, and final texture from its maximum annealing temperature to said temannealing at a maximum temperature of 2150F. perature below 1600F and above 1000F at a rate The heat was tested for permeability. A permeability which is no faster than one wherein the steel is cooled of I853 (G/O at 10 oersteds was recorded. in a static atmosphere or in a continuous processing It will be apparent to those skilled in the art that the line where there is some relative motion between the novel principles of the invention disclosed herein in atmosphere and the steel, although the only deliberate connection with specific examples thereof will suggest motion is that imparted to the steel. various other modifications and applications of the 5. An improvement according to claim 1, wherein same. It is accordingly desired that in construing the said steel is cooled to a temperature at least as low as breadth of the appended claims they shall not be lim- 500F from a temperature below l700F and above ited to the specific examples of the invention described 750F with a gaseous stream. herein. 6. An improvement according to claim 1, wherein We claim: said steel is cooled to a temperature at least as low as 1. In a process for producing electromagnetic silicon 500F from a temperature below l700F and above steel having a cube-on-edge orientation and a permea- 750F with a liquid quenching medium. bility of at least 1850 (6/0,) at 10 oersteds, which pro- 7. An improvement according to claim 1, wherein cess includes the steps of: preparing a melt of silicon said steel is air cooled to said temperature below steel; casting said steel; hot rolling said steel into a hot l700F and above 750F. rolled band; subjecting said steel to at least one cold 8. An improvement according to claim 3, wherein rolling; subjecting said steel to a final annealing prior to said steel is cooled to a temperature at least as low as the final cold rolling; decarburizing said steel; and final 500F from a temperature below l700F and above texture annealing said steel; the improvement compris- 750F with a gaseous stream. ing the steps of carrying out said final anneal prior to 9. An improvement according to claim 3, wherein the final cold rolling at a temperature of from l400 to said steel is cooled to a temperature at least as low as 2150F for a period of from l5 seconds to 2 hours; 500F from a temperature below l700F and above cooling said steel from a temperature below l700F 750F with a liquid quenching medium. and above 750F to a temperature at least as low as 10. An improvement according to claim 3, wherein 500F with a liquid quenching medium or gaseous said steel is air cooled to said temperature below stream and from its maximum annealing temperature l700F and above 750F.

to said temperature below l700F and above 750F at a rate which is no faster than one wherein the steel is cooled in a static atmosphere or in a continuous pro- 11. An improvement according to claim 1, wherein said final anneal prior to the final cold rolling is carried out subsequent to an initial cold rolling.

13. An improvement according to claim 1, wherein the cooled steel is cold rolled at a reduction of at least 14. An improvement according to claim 3, wherein the cooled steel is cold rolled at a reduction of at least 85%.

15. An improvement according to claim 1, wherein said final anneal prior to the final cold rolling is applied to a hot rolled band. 

1. IN A PROCESS FOR PRODUCING ELECTROMAGNETIC SILICON STEEL HAVING A CUBE-ON-EDGE ORIENTATION AND A PERMEABILITY OF AT LEAST 1850 (G/OE) AT 10 OERSTEDS, WHICH PROCESS INCLUDES THE STEPS OF: PREPARING A MELT OF SILICON STEEL, CASTING SAID STEEL, HOT ROLLING SAID STEEL INTO A HOT ROLLED BAND, SUBJECTING SAID STEEL TO AT LEAST ONE COLD ROLLING, SUBJECTING AID STEEL TO A FINAL ANNEALING PRIOR TO THE FINAL COLD ROLLING, DECARBURIZING SAID STEEL, AND FINAL TEXTURE ANNEALING SAID STEEL, THE IMPROVEMENT COMPRISING THE STEPS OF CARRYING OUT SAID FINAL ANNEAL PRIOR TO THE FINAL COLD ROLLING AT A TEMPERATURE OF FROM 1400* TO 2150*F FOR A PERIOD OF FROM 15 SECONDS TO 2 HOURS; COOLING SAID STEEL FROM A TEMPERATURE BELOW 1700*F AND ABOVE 750*F TO A TEMPERATURE AT LEAST AS LOW AS 500*F WITH A LIQUID QUENCHING MEDIUN OR GASEOUS STREAM AND FROMITS MAXIMUM ANNEALING TEMPERATURE TO SAID TEMPERATURE BELOW 1700*F AND ABOVE 750*F AT A RATE WHICH IS NO FASTER THAN ONE WHEREIN THE STEEL IS COOLED IN A STATIC ATMOSPHERE OR IN A CONTINUOUS PRECESSING LINE WHERE THERE IS SOME RELATIVE MOTION BETWEEN THE ATMOSPHERE AND THE STEEL, ALTHOUGH THE OBLY DELIBERATE MOTION IS THAT IMPARTED TO THE STEEL; AND COLK ROLLING THE COOLED STEEL AT A REDUCTION OF AT LEAST 80%; SAID MELT CONSISTING ESSENTIALLY OF, BY WEIGHT, UP TO 0.07% CARBON, FRO, 2.60 TO 4.0% SILICON, FROM 0.03 TO 0.24% MANGANESE, AT LEAST 0.01% SELENIUM, FROM 0.01 TO O.09% OF MATERIAL FROM THE GROUP CONSISTING OF SULFUR AND SELENIUM, FROM 0.015 TO 0.04% ALUMINUM, UP TO 0.02% NITROGEN, FROM 0.1 TO 0.5% COPPER, BALANCE IRON.
 2. An improvement according to claim 1, wherein said steel is cooled from a temperature below 1600*F and above 1000*F to a temperature at least as low as 500*F with a liquid quenching medium or gaseous stream and from its maximum annealing temperature to said temperature below 1600*F and above 1000*F at a rate which is no faster than one wherein the steel is cooled in a static atmosphere or in a continuous processing line where there is some relative motion between the atmosphere and the steel, although the only deliberate motion is that imparted to the steel.
 3. An improvement according to claim 1, wherein said final anneal prior to the final cold rolling is at a temperature of from 1800* to 2125*F.
 4. An improvement according to claim 3, wherein said steel is cooled from a temperature 1600*F and above 1000*F to a temperature at least as low as 500*F with a liquid quenching medium or gaseous stream and from its maximum annealing temperature to said temperature below 1600*F and above 1000*F at a rate which is no faster than one wherein the steel is cooled in a static atmosphere or in a continuous processing line where there is some relative motion between the atmosphere and the steel, although the only deliberate motion is that imparted to the steel.
 5. An improvement according to claim 1, wherein said steel is cooled to a temperature at least as low as 500*F from a temperature below 1700*F and above 750*F with a gaseous stream.
 6. An improvement according to claim 1, wherein said steel is cooled to a temperature at least as low as 500*F froM a temperature below 1700*F and above 750*F with a liquid quenching medium.
 7. An improvement according to claim 1, wherein said steel is air cooled to said temperature below 1700*F and above 750*F.
 8. An improvement according to claim 3, wherein said steel is cooled to a temperature at least as low as 500*F from a temperature below 1700*F and above 750*F with a gaseous stream.
 9. An improvement according to claim 3, wherein said steel is cooled to a temperature at least as low as 500*F from a temperature below 1700*F and above 750*F with a liquid quenching medium.
 10. An improvement according to claim 3, wherein said steel is air cooled to said temperature below 1700*F and above 750*F.
 11. An improvement according to claim 1, wherein said final anneal prior to the final cold rolling is carried out subsequent to an initial cold rolling.
 12. An improvment according to claim 1, wherein said steel consists essentially of, by weight, from 0.02 to 0.07% carbon, from 2.65 to 3.25% silicon, from 0.05 to 0.20% manganese, at least 0.02% selenium, from 0.02 to 0.07% of material from the group consisting of sulfur and selenium, from 0.015 to 0.04% aluminum, from 0.0030 to 0.0090% nitrogen, from 0.1 to 0.4% copper, balance iron.
 13. An improvement according to claim 1, wherein the cooled steel is cold rolled at a reduction of at least 85%.
 14. An improvement according to claim 3, wherein the cooled steel is cold rolled at a reduction of at least 85%.
 15. An improvement according to claim 1, wherein said final anneal prior to the final cold rolling is applied to a hot rolled band. 